Use bitmap subset for comparison in texture_domain_effect GMs.

This used to do 2 texel subset draws. The second draw tested a
non-identity local matrix. Now the first draw exercises local matrix and
the second draws with a proxy that represents just the bitmap subset to
give a better basis for comparison.

Change-Id: Ia41330598626c8cc656fd1ca2e289c8184847807
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/266616
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
1 file changed